1. Field of the Invention
The present invention relates to a resource reservation protocol (RSVP) substitute reply router, a RSVP substitute reply system and a RSVP substitute reply method to be used in the same. More particularly, the invention relates to a network of RSVP used for quality of service (QoS) guarantee.
2. Description of the Related Art
In the recent years, speeding up of an access line called as last one mile has been progressed quickly. Even in consumers, it has been becoming to easily use high speed access line, such as CATV (CAble TeleVision), ADSL (Asymmetric Digital Subscriber Line), FTTH (Fiber To The Home) or the like. Since high speed access lines become available for large number of users, service providers providing image broadcasting service which has been impossible in the conventional low speed line, are coming into services.
In such image broadcasting services, currently, service is provided in best effort manner relying on a high speed backbone of Internet. However, in order to put high quality image broadcasting into practice, QoS (Quality of Server) guarantee (acquiring of band, guarantee of delay) in broadcasting path becomes necessary. On the other hand, for providing image broadcasting to the users as business, QoS guarantee is inherent upon image broadcasting.
Currently, as a protocol to be used for QoS guarantee in Internet, RSVP has been standardized. This is a protocol for sequentially reserving resource of routers through which RSVP messages pass, by exchanging of RSVP messages between both hosts transmitting and receiving data in RSVP.
A procedure of forgoing RSVP is shown in FIG. 15. In RSVP procedure, an RSVP recognition source host 34 transmits a Path message indicative of traffic characteristics to an RSVP recognition recipient host 31, as shown in FIG. 15. The Path message reaches the RSVP recognition recipient host 31 via switches 33 and 32 (RSVP compatible routers) on the path and a backbone network (RSVP network) 200.
When the Path message is received, the RSVP recognition recipient host 31 transmits a Resv (reserve) message indicating a desired QoS to the switch 32 immediately before on the foregoing path. The switch 32 reserves a resource in the switch 32 and transfers the Resv message to the switch 33 of the preceding stage on the path for guarantee QoS indicated in the Resv message. Even in the switch 33, a resource in the switch 33 is reserved and transfers the Resv message to the RSVP recognition source host 34 in order to guarantee QoS indicated in the Resv message. At a timing where the Resv message arrives to the RSVP recognition source host 34, all of the resources on the path are reserved in order to guarantee QoS indicated in the Resv message.
For the RSVP recognition recipient host 31, data of high quality image or the like is transmitted using the resources reserved through the foregoing process. However, once transmission of these data is completed, reservation of resource is released in the switches 33 and 32 by feeding a Path Tear message to the RSVP recognition recipient host 31 via the switches 33 and 32 on the path and the backbone network 200. It should be noted that a Path message is fed with a preliminarily set predetermined interval from the RSVP recognition source host 34. In response to the Path message, the Resv message is returned with a predetermined interval from the RSVP recognition recipient host 31. Accordingly, when the Path Tear message is lost in the midway, judgment is made that reservation is released to release the reserved resource when the Path message does not arrive even after the predetermined interval.
However, RSVP is a protocol having large process load. In a router on the Internet, RSVP is generally not supported. On the other hand, since RSVP is not supported on Internet, RSVP is not installed in many of the existing communication hosts. It should be appreciated that, toward the future, in order to provide a service for the application requiring QoS guarantee represented by foregoing image broadcasting, it is expected that RSVP router may be arranged in particular range [inside of one ISP (Internet Service Provider)]. At this time, a problem is arisen in the communication host not adapted to RSVP.
Even if the RSVP router is arranged on the network, effect of RSVP cannot be obtained unless RSVP is installed in the communication host transmitting and receiving data. Even in the communication host not adapted to RSVP, it has been desired a method to obtain the effect of QoS guarantee of the RSVP network. Even in the communication host not adapted to RSVP, as an example of the system where to obtain QoS guarantee effect of RSVP network, there is a system of service of RSVP proxy service (for example, see Japanese Unexamined Patent Publication No. 2001-352347 (pages 4 to 5, FIG. 1).
The RSVP proxy service is constructed with RSVP none recognition recipient host 35, switches 32 and 33, the RSVP recognition source host 34 and a backbone network (RSVP network) 200, as shown in FIG. 16. In the RSVP proxy service construction set forth above, the RSVP recognition source host 34 transmits the Path message of RSVP to the RSVP none recognition recipient host 35 in order to certainly obtain QoS of the transmission path of data packet.
The Path message transmitted from the RSVP recognizing source host 34 is transferred to the switch 33, at first, and is further transferred to the switch 32 via the backbone network (RSVP network) 200. At this time, when the Path message for particular destination is received, it is set to make RSVP reception side host proxy function in effect in the switch 32.
The switch 32 receiving the Path message checks a destination of the Path message to make judgment whether RSVP reception side host proxy function of the switch 32 is to be operated or not. When judgment is made that the RSVP reception side host proxy function is to be in effect, the switch 32 does not transfer the Path message to the RSVP none recognition recipient host 35 and instead the switch 32 transmits the Resv message toward the RSVP recognition source host 34 side to reserve the resource of the path up to the RSVP recognition source host 34 to guarantee QoS of the data packet transmitted from the RSVP recognition source host 34.
However, in the network of the conventional RSVP, since destination address is used as a condition for operating the RSVP reception side host proxy function, it becomes necessary to preliminarily register objective address to the switch 32.
Therefore, in the conventional network of RSVP, when the communication hosts not compatible with RSVP and communication hosts compatible with RSVP are present in the data reception side network in admixing manner, destination addresses to be registered in the switch 32 is increased to make management complicate. Particularly, when addresses of communication hosts are varied for rearrangement or other reason, addresses registered in the switch 32 has to be varied.